Heretofore, in graphic arts and medical fields, effluent generated by wet processing of image forming materials has resulted in problems in view of workability. In recent years, in view of environmental protection and space saving, highly demanded has been a decrease in processing effluent. Consequently, demanded have been technologies in regard to photothermographic materials for photographic use, which enable efficient exposure employing laser image setters and laser imagers, and enable forming clear black images at high resolution. Known as such technology are silver salt photothermographic dry imaging materials which incorporate a support having thereon organic silver salts, photosensitive silver halide grains, reducing agents, and binders (refer, for example, to Patent Documents 1 and 2, and Non-Patent Document 1).
These silver salt photothermographic dry imaging materials form photographic images via heat development, and incorporate reducible silver sources (such as organic silver salts), photosensitive silver halide, reducing agents, and if desired, toners which control silver tone, all of which are in a dispersed state, commonly in an (organic) binder matrix. The above silver salt photothermographic dry imaging materials are stable at normal temperature. However, when heated to relatively high temperatures (for example, 80-140° C.) after exposure, they are developed into visible images. Via heating, silver is formed through the oxidation-reduction reaction between the organic silver salts (which function as an oxidizing agent) and the reducing agents. This oxidation-reduction reaction is promoted by catalytic action of latent images formed on silver halide by exposure. Silver, which is formed via the reaction of organic silver salts in the exposed area provides a black image with respect to the unexposed areas, whereby an image is formed. The above reaction process proceeds without any supply of a processing liquid such as water from the exterior.
Such silver salt photothemographic dry imaging materials are commonly prepared in such a manner that layers such as emulsion layers, if desired, interlayers, a protective layer, a backing layer, an antihalation layer, or an antistatic layer, which constitute the above silver salt photothermographic dry imaging materials, are variously combined and applied onto a support such as a plastic film. The silver salt photothermographic dry imaging materials are frequently adversely affected by contact with various apparatuses and contact between the front and back sides during winding, unwinding, and conveyance in each production process such as coating, drying and packaging. Examples include the formation of scratches and sliding abrasion on the surface of silver salt photothermographic dry imaging materials, as well as degradation of conveying properties of silver salt photothermographic dry imaging materials in a processing apparatus.
On the other hand, it is required that silver salt photothermographic dry imaging materials are provided with specific characteristics for heat development. For example, since humidity in the interior of a thermal processor employed for heat development becomes excessively low due to the increase in temperature to tend to generate static electricity, whereby problems occur in which it is not possible to separately convey each of the silver salt photothermographic dry imaging materials and conveying problems such as jamming tend to result.
In order to overcome the above drawbacks, disclosed are a method in which improvement is achieved employing alkylsilane compounds having at least 8 carbon atoms (refer, for example, to Patent Document 3), and a method employing sulfur based or ester based lubricants (refer, for example, to Patent Document 4). However, both methods result in problems in which photographic performance is adversely affected, that is, specifically, image tone is degraded. Further, problems surface in which the interior of a thermal processor at high temperature is stained and it is not possible to sufficiently provide lubrication properties at high temperatures.
To overcome the above drawback, disclosed is a method employing inorganic solid lubricants (refer, for example, to Patent Document 5). Recently, however, the conveying rate in thermal processors and the processing rate in automatic processors have been markedly increased, and it is difficult to state that the above proposed method has overcome the drawback. Consequently, it has been further demanded to improve lubrication properties.
Further, to overcome these drawbacks, provided are heat developable photosensitive materials in which crystalline metal oxides, which exhibit less humidity dependence of electrical conductivity, are employed (refer, for example, to Patent Documents 6-9). In these heat developable photosensitive materials, employed are ionic surface active agents and hygroscopic polysilicic acid in the outermost layer, whereby these components are easily affected by humidity to occasionally result in variation of surface resistivity. Further, a more critical drawback has been noted in which during storage in such a state that heat developable photosensitive materials are brought into contact with each other, these surface active agents are transferred to the surface opposite the incorporation layer due to relatively small molecules, whereby photographic performance and lubrication properties are adversely affected.
(Patent Document 1) U.S. Pat. No. 3,152,904
(Patent Document 2) U.S. Pat. No. 3,487,075
(Patent Document 3) U.S. Pat. No. 36,020,117
(Patent Document 4) Japanese Patent Publication Open to Public Inspection (hereinafter referred to as JP-A) No. 2001-005137
(Patent Document 5) JP-A No. 2002-116520
(Patent Document 6) JP-A No. 7-49543 (Examples)
(Patent Document 7) JP-A No. 8-43988 (Examples)
(Patent Document 8) JP-A No. 11-24200 (Examples)
(Patent Document 9) JP-A No. 2000-162731 (Claim 1 and Examples)
(Non-patent Document 1) D. Morgan, “Dry Silver Photographic Materials” Handbook of Imaging Materials, Marcel Dekker, Inc., page 48, 1991